/Engine/Source/Runtime/Engine/Classes/Kismet/KismetMathLibrary.h
If you don't care about preserving the up vector and just want the most direct rotation, you can use the faster 'FindBetweenVectors(ForwardVector, YourVector)' or 'FindBetweenNormals(...)' if you know the vector is of unit length.
Quaternion from the Vector's direction, without any roll.
static FQuat Conv_Vector4ToQuaternion ( const FVector4 & InVec )